Recommendations of the International Task Force for Disease
Eradication

Summary

This report summarizes the conclusions of the International
Task Force for Disease Eradication (ITFDE), a group of scientists
who were convened by a secretariat at the Carter Center of Emory
University six times during 1989-1992. The purpose of the ITFDE was
to establish criteria and apply them systematically to evaluate the
potential eradicability of other diseases in the aftermath of the
Smallpox Eradication Program. The ITFDE defined eradication as
"reduction of the worldwide incidence of a disease to zero as a
result of deliberate efforts, obviating the necessity for further
control measures."

The names of the members of the ITFDE, the criteria they
developed and used, and summaries of the papers that were presented
to the ITFDE by various experts are included in this report, as
well as a brief history of the concept of disease eradication since
the late 19th century. The ITFDE considered more than 90 diseases
and reviewed 30 of these in depth, including one noninfectious
disease. It concluded that six diseases -- dracunculiasis,
poliomyelitis, mumps, rubella, lymphatic filariasis, and
cysticercosis -- could probably be eradicated by using current
technology. It also concluded that manifestations of seven other
diseases could be "eliminated," and it noted critical research
needs that, if realized, might permit other diseases to be
eradicated eventually. The successful eradication of smallpox in
1977 and the ongoing campaigns to eradicate dracunculiasis by 1995
and poliomyelitis by 2000 should ensure that eradication of
selected diseases will continue to be used as a powerful tool of
international public health.

INTRODUCTION

This issue of MMWR Recommendations and Reports consolidates
the deliberations of the International Task Force for Disease
Eradication (ITFDE), which was convened six times from 1989 through
1992 to evaluate diseases as potential candidates for global
eradication (1-7). CDC supports the findings in this report, which
indicate a need for greater recognition of the potential to
eradicate targeted diseases. Three reports, covering results of the
first five meetings, were published previously in the MMWR (1-3),
and reprinted in WHO's Weekly Epidemiological Record (4-6). A
report of the sixth meeting was also published in the Weekly
Epidemiological Record (7).

Eradication is defined as reduction of the worldwide incidence
of a disease to zero as a result of deliberate efforts, obviating
the necessity for further control measures. The criteria that the
ITFDE developed and their conclusions after reviewing more than 90
diseases are presented in this report.

An important part of the work was to help identify key
impediments to improved prevention and control of the diseases
under discussion, even if the disease was not considered to have
potential as a candidate for eradication. One such "noneradication
outcome" was the impetus that the members of the ITFDE gave to
initiating a demonstration project to control intestinal parasites
among schoolchildren in Ghana.

A SPECTRUM OF DISEASE CONTROL

Between the extremes of disease "control" (reduction in
incidence and/or prevalence) and "eradication," several
intermediate levels of impact on diseases may be described. The
term "elimination" is sometimes used synonymously with
"eradication," but it refers to a single country, continent, or
other limited geographic area, rather than global eradication. True
eradication usually entails eliminating the microorganism itself or
removing it completely from nature, as in the case of smallpox
virus, which now exists only in storage in two laboratories. It is
also theoretically possible to "eliminate" a disease in humans
while the microbe remains at large, as in the case of neonatal
tetanus, for which the World Health Organization (WHO) in 1989
declared a goal of global elimination by 1995.

Although a disease itself may remain, a particularly
undesirable clinical manifestation of it may be prevented entirely.
Examples of this level of eradication are the use of chemotherapy
with ivermectin to eliminate blindness resulting from
onchocerciasis and of vitamin A to eliminate xerophthalmia.
Eliminating transmission of a disease may also be considered, as in
the case of yaws, the late noninfectious clinical manifestations
remain of which but are not a danger to others. Finally,
"elimination" can be defined as control of the manifestations of a
disease so that the disease is no longer considered "a public
health problem," as an arbitrarily defined qualitative or
quantitative level of disease control (e.g., WHO's goal of
eliminating leprosy by the year 2000, which is defined as reducing
its incidence to a level below one case per 10,000 population).

Even as smallpox was being eradicated, public health
authorities recognized that the eradication campaign was possible
because of several important characteristics of smallpox and the
smallpox vaccine. Smallpox was epidemiologically vulnerable because
it had no natural reservoir in species other than humans; the
infection was obvious and usually easily diagnosed; the duration
and intensity of infectiousness were limited; persons who recovered
were immune for life and often permanently scarred; and its
transmission was highly seasonal in many areas. The vaccine was
safe, effective even in newborns, inexpensive, easily administered,
and stable in tropical climates; its effects were long-lasting; and
vaccinated persons had a recognizable scar (8).

As a tool for international public health, eradication of
well-chosen diseases has two advantages:

Eradication is permanent, as are its benefits. In contrast, the
costs of control programs continue indefinitely, along with the
risks of future exacerbation of the disease following a disaster of
natural or human origin. For some diseases, achieving control would
require only marginally less effort than that needed to achieve
eradication, but control measures would need to be continued
indefinitely. Eradication is the ultimate "sustainable" improvement
in public health. The recent reimportation of wild poliovirus into
the Western Hemisphere more than 18 months since its last known
previous occurrence (9) and the possibility of changes in other
pathogens in ways that can make them impervious to once-effective
control measures (10) would not be of concern had successful
eradication campaigns taken place. (Fear of the consequences of
emerging resistance of malarial mosquito vectors and of the
parasite itself was partly responsible for the precipitous decision
in the 1950s to eradicate malaria.)

A time-limited goal of eradication allows mobilization of
support
for a concentrated effort more readily than does a control program-
-both within countries where the disease is endemic and
internationally. If developed countries have to spend resources to
prevent or control importations of the disease (e.g.,
poliomyelitis, smallpox), such countries have additional incentive
to help support an eradication campaign.

Participation in a successful eradication campaign can also be
effective in improving the morale and performance of workers in
public health, although this potential benefit can also be derived
from a control program. An eradication campaign requires complete
surveillance, rigorous administration, and operational research to
a degree that may not be necessary in a control program because the
standard of success in an eradication program is unambiguous and
uncompromising. Another requirement of an eradication campaign may
be funding to support measures to eliminate a minor focus of
disease from a country where the disease has limited impact and
does not constitute a national priority.

The potential negative effects of an eradication campaign,
especially an unsuccessful one, must also be weighed. One study
stressed the economic consequences and the potential negative
impact on broader public health programs (11). The possible effects
of competition for scarce resources and the political implications
are among the factors that should be considered (12).

The ITFDE developed specific criteria to consider the
potential for eradication of diseases other than smallpox
(Table_1).
These criteria acknowledge that combinations of favorable
characteristics other than those that obtained for smallpox might
permit other diseases to be eradicated. They generally include
elements similar to previously suggested criteria (11,12); however,
the criteria of the ITFDE distinguish scientific feasibility from
sociopolitical feasibility.

A BRIEF HISTORY OF DISEASE ERADICATION

Every friend of humanity must look with pleasure on this
discovery {smallpox vaccination}, by which one evil more is
withdrawn from the condition of man; and must contemplate the
possibility that future improvements and discoveries may still more
and more lessen the catalogue of evils.
Thomas Jefferson, 1800

The eventual eradication of smallpox as a result of the use of
Jennerian vaccination was predicted by Edward Jenner, as well as by
Thomas Jefferson, in the early 19th century. Following the
emergence of the germ theory and more systematic approaches to
disease control in the mid-19th century, the concept of eradication
of a disease first became popular briefly around the turn of the
century. Milestones in the history of disease eradication over the
years have been summarized (Table_2). Contagious
pleuropneumonia of
cattle, a disease that had been imported into the United States in
1843, was declared eradicated from the country in 1892, following
a 5-year, $2-million campaign to identify and slaughter infected
animals (13).

The Rockefeller Foundation began campaigns to eradicate
hookworm in 1907 and yellow fever in 1915. Both these campaigns
against diseases of humans failed: the hookworm campaign because
mass treatment of affected populations with anthelmintic therapy
reduced the severity of individual infections but rarely eliminated
them and thus did not prevent rapid reinfection (14); and the
campaign against yellow fever because of the previously unknown,
inaccessible cycle of disease among nonhuman primates living in
forests (15). Acceptance of the concept of eradication declined
during the late 1920s and early 1930s, after the futility of the
eradication of hookworm and yellow fever was recognized.

The concept became popular again in the late 1940s, following
the elimination of Anopheles gambiae mosquitoes from Brazil and
Egypt, the elimination of malaria from Sardinia, reductions in the
prevalence of yaws in Haiti, and the introduction of a stable
freeze-dried vaccine against smallpox (13,15). By 1955, WHO had
declared goals of global eradication of yaws and malaria, and in
1958 it adopted the goal of smallpox eradication as well. The yaws
campaign failed, partly because persons with inapparent latent
cases were not adequately treated, in addition to persons with
clinical disease. Many such latent infections relapsed to produce
infectious lesions soon after mass treatment teams visited a
community. Later, disease-specific control measures were withdrawn
prematurely, allowing the infection to reappear in several areas
(16).

Failure to achieve malaria eradication, after an expenditure
estimated at $1.4 billion during the period 1955-1965, brought the
concept of eradication into disfavor again (17). Resistance of some
vectors to insecticides and of some parasites to treatment, the
unexpected diversity and tenacity of some vectors, administrative
shortcomings, and rising costs were all factors in the decision to
abandon the goal of eradicating malaria (18). (WHO officially
revised the goal to one of control in 1969.) The achievement of
global smallpox eradication in 1977 and its official certification
by WHO in 1980 did not at first bring about the acceptance of the
concept of eradication. Concerns were raised that a new eradication
effort might detract from efforts to focus attention on the need
for developing comprehensive primary health services, rather than
focusing on one or two diseases (19). However, several diseases
(e.g., schistosomiasis, rotavirus diarrhea, brucellosis, and
leprosy) that were then being considered as possible targets for
global eradication did not have potential for success given the
current technology. Several reports and conferences have considered
the potential for eradicating other diseases, of which
poliomyelitis, mumps, and rubella were among those most frequently
cited (18,20-23). Reports in 1980 and 1985 both concluded that no
other major disease was then a potential candidate to be targeted
by a global eradication campaign (18,20).

After the concept of eradication was accepted again in the
late 1980s, some observers considered a disease to be unsuitable
for eradication to the extent that it differed from smallpox or
that the intervention against it differed from smallpox vaccine
(24). In this third period of acceptance, WHO has targeted
dracunculiasis and poliomyelitis for eradication.

SUMMARY OF THE ITFDE DELIBERATIONS

Ninety-four infectious diseases were screened by the ITFDE
(Appendix 1). The ITFDE considered 29 infectious diseases in depth,
as well as one noninfectious condition (iodine deficiency). The
latter condition was chosen in part to enable the ITFDE to apply
the criteria it had developed to at least one noninfectious
candidate for eradication, as an example in principle. Some
infectious diseases that were already proposed for eradication by
WHO or by other organizations or countries were considered by the
ITFDE before the list was completed. Those diseases were not
included in the list of diseases subjected to preliminary screening
by the ITFDE.

Of the ninety-four diseases that were screened, the ITFDE
concluded that six were potentially eradicable: dracunculiasis
(Guinea worm disease), poliomyelitis, mumps, rubella, lymphatic
filariasis, and taeniasis/cysticercosis (pork tapeworm). Of these,
only the first two had already been targeted for global
eradication. The ITFDE also noted that seven other conditions or
clinical manifestations of diseases might be eliminated: blindness
from onchocerciasis, urban rabies, transmission of yaws and other
endemic treponematoses, transmission of hepatitis B, transmission
of neonatal tetanus, blindness from trachoma, and iodine deficiency
disorders. Key obstacles to eradication, elimination, or improved
control were also highlighted by the ITFDE in its discussions of
the 30 diseases that it considered in depth (Table_3).

Summaries * of the 30 background papers that were presented to
the ITFDE appear below. At least two of the papers prepared for
meetings of the ITFDE have been published or accepted for
publication (25,26).

Diseases Targeted for Eradication

Dracunculiasis (Guinea Worm Disease)

Dracunculus medinensis now affects as many as 2 million
persons in India, Pakistan, and approximately 16 African countries,
where greater than 100 million persons are at risk for the disease
(27). Persons are infected by drinking water containing immature
forms of the parasite. A year later, the female adult worms, each
about 1 meter long, emerge through the skin, causing crippling pain
that prevents these persons from carrying out their daily
activities for periods of weeks or months. When infected persons
wade or bathe, the immature forms of the worms enter the water to
continue the cycle. Most infections, which induce no immunity and
may affect over half a village's population during planting or
harvest seasons, are not fatal, but secondary bacterial infections
may be life threatening.

Dracunculiasis can be prevented by teaching residents of areas
where the disease is endemic to prevent affected persons from
entering drinking water sources and to boil or filter their
drinking water; by providing water from safe sources such as wells;
or by using a chemical to kill the water fleas that harbor the
larval parasite. The global eradication campaign began with the
International Drinking Water Supply and Sanitation Decade (1981-
1990). In 1986, the World Health Assembly (WHA) adopted the goal of
eliminating dracunculiasis. The goal of eradicating dracunculiasis
by 1995 was declared by the WHA in 1991. No technical barriers
remain, but more social mobilization and funding are needed.

Poliomyelitis

WHO estimates that about 100,000 cases of paralytic
poliomyelitis still occur annually worldwide, mostly in Asia and
Africa, with approximately 10,000 deaths (28). For every paralytic
case, 100 asymptomatic persons carry the virus and can infect
others. This virus is transmitted mostly by airborne droplets from
infected persons. Persons who recover are immune. The incidence of
poliomyelitis has been reduced as a result of the increases in
vaccination rates during the drive to vaccinate at least 80% of the
world's infants by December 1990. (About 85% were vaccinated
against poliomyelitis.) Protection against poliomyelitis requires
three or four injections or oral doses of vaccine.

In 1985, the Pan American Health Organization declared the
goal of eliminating poliomyelitis from the Americas by 1990 -- a
goal
that apparently has been achieved, with the final cases reported
from Peru in September 1991. In 1988, the WHA declared the goal of
eradicating poliomyelitis from the world by the year 2000. WHO now
estimates that the external costs of eradicating poliomyelitis will
be about U.S. $1.1 billion. Poliomyelitis eradication appears to be
technically feasible and would be facilitated by development of a
vaccine that requires fewer doses or is more heat stable. The most
urgent need is for adequate supplies of the existing vaccine and
additional funding.

Diseases that Could Potentially Be Eradicated

Lymphatic Filariasis

Lymphatic filariasis is caused by any of three species of
parasitic worms: Wuchereria bancrofti, Brugia malayi, or Brugia
timori (29). Nearly 80 million persons are infected in the tropics
and subtropics after long exposure to the bites of certain
mosquitoes. Adult worms can live in the lymphatic system for 10-15
years. Female worms discharge microfilariae into the blood, where
they can infect other mosquitoes and through them, other humans.
Humans are the only reservoir of infection, except for B. malayi,
which has a reservoir in nonhuman primates that does not appear to
contribute to transmission to humans. Complications include
swellings of limbs or other appendages (elephantiasis) from
interaction of the parasite with the host's immune system. Many
infected persons have no symptoms, and the infection is not fatal.

The impact of this infection and disease has been reduced in
several areas by mass treatment of populations with
diethylcarbamazine (DEC). DEC also has some adulticide effect.
Ivermectin is another effective drug that is inexpensive and easily
administered. Some side effects may occur after either drug, which
may be administered once a year. Improved tests are needed for
detecting and monitoring infection. More data are needed about
costs of intervention and the effects of ivermectin mass treatment
of onchocerciasis on filariasis in West Africa. This disease may be
eradicable by using single doses of invermectin, DEC, and salt
containing DEC.

Mumps

Mumps is a viral disease that occurs worldwide and usually
affects children (30). It is characterized by fever and painful
swelling of the parotid salivary glands. Complications may include
orchitis, meningitis, and encephalitis, but inapparent infections
are common. Spread by direct contact and airborne droplets, mumps
is less contagious than measles or varicella. Humans are the only
reservoir of this infection, which confers lifelong immunity. The
global impact of mumps is unknown but is perceived to be less than
that caused by rubella.

Mumps vaccine is highly effective in a single dose when
administered after 1 year of age. Most commonly the vaccine is
administered in combination with rubella and measles vaccines as
MMR vaccine, which requires refrigeration and is administered by
injection. Several countries in the Americas, Western Pacific, and
Europe include MMR vaccine among the standard group of vaccines
recommended for children. Mumps meningitis reportedly disappeared
in Cuba following increased vaccination of young children with MMR
vaccine. Additional studies are needed to evaluate the impact of
mumps (and rubella) in developing countries, as well as the impact
of mumps vaccine, including effects of underimmunization (partial
suppression of wild virus). The potential synergy of a combined
campaign against mumps along with measles and rubella is perhaps
the factor most favoring its eradication. Mumps is probably
eradicable with MMR vaccine.

Rubella

Rubella causes mild disease when acquired postnatally, but it
can cause severe birth defects in at least 20%-25% of infants born
to women infected during the first trimester of pregnancy (31). It
occurs worldwide. Most infections are subclinical, but these do not
appear to play an important role in transmission. Little is known
of the disease's impact in developing countries, but serologic
surveys indicate that most African children are immune to the virus
by their tenth birthday. There is no animal reservoir of infection,
and this disease is less contagious than rubeola.

The live-virus vaccine is effective in a single dose and is
often administered as part of a triple vaccine against measles,
mumps, and rubella (MMR), so that its marginal cost is extremely
small. Use of the vaccine has reduced or interrupted transmisssion
in several countries, including Cuba, Sweden, Finland, and the
United States. Immunization strategies include universal
vaccination of children and susceptible women of childbearing age.
The potential for increasing susceptibility in women by
underimmunization of children (partial suppression of wild virus)
must be avoided. An increasing number of countries include MMR
vaccine in their routine immunization services. Rubella can be
eradicated, and the availability of the MMR combined vaccine has
lowered the marginal costs of rubella eradication. More data
regarding rubella's impact in developing countries are needed. A
strategy that does not inadvertently increase the number of
susceptible women should be used.

Taeniasis/Cysticercosis (Pork Tapeworm)

Human beings are the only definitive hosts of Taenia saginata
(beef tapeworm) and Taenia solium (pork tapeworm) (26). The beef
tapeworm is associated with cattle husbandry; it is the more
widespread of the two and is increasing in Europe. Both species are
most prevalent in Latin America, Asia, and Africa. Humans are
infected by eating inadequately cooked, contaminated beef or pork.
The eggs of T. solium are also infective to humans, who may develop
a life-threatening dissemination of larvae to cause cysts in
various tissues. Epileptic seizures are a major manifestation when
such cysts occur in the brain. Approximately 50 million persons are
infected with both parasites; some 50,000 die of cysticercosis
annually.

Effective means now exist for surveillance to identify foci of
transmission of T. solium and for mass treatment of humans (e.g.,
praziquantel and niclosamide) to help eliminate such foci. This
parasite causes a substantial economic burden to the pork industry.
T. solium has disappeared gradually from most European countries
even without targeted control measures. Research priorities include
development of a more sensitive diagnostic test for use in pigs and
a better way to identify infected persons. T. solium cysticercosis
is potentially eradicable through surveillance and available
interventions, but such feasibility needs to be demonstrated in a
sizable geographic area.

Diseases of which Some Aspect Could Be Eliminated

Hepatitis B

Hepatitis B is a viral disease that is responsible for more
than 250,000 deaths per year worldwide (32). High incidences are
found in Alaska and other arctic areas, Africa, China, Southeast
Asia, and the Amazon. Many infections are asymptomatic. Hepatitis
B is transmitted in early childhood, often perinatally from mother
to infant; sexual and other transmission by direct contact also
occur. About 5% of infections occur in utero. More than two thirds
of persons infected in infancy become persistent carriers of the
virus. Deaths result from liver cancer or chronic liver disease,
including cirrhosis.

A vaccine to prevent hepatitis B was introduced in the late
1970s. Three doses are required, beginning at birth or in early
infancy in areas where the disease is highly endemic. Some
countries have begun routine mass vaccinations of infants against
hepatitis B as a part of their Expanded Programme on Immunization.
An alternative approach is to vaccinate only infants of infected
mothers who have been identified by prior screening. At the current
cost of U.S. $7.60 per dose of vaccine, hepatitis B could be
eventually eliminated from the United States at a cost of about
$120 million per year, compared with an estimated annual cost of
$750 million for treating persons who contract the disease.
Reduction of disease would not begin to be evident for about 15
years. It is not possible to eradicate hepatitis B now, but it is
technically feasible to eliminate its transmission by universal
vaccination programs.

Iodine Deficiency Disorders

More than a billion persons are at risk for this noninfectious
condition, which is the leading preventable cause of intellectual
impairment in the world (33). The number of persons affected is
unknown, but prevalences of the most severe form, cretinism, often
reach 3%-15% in areas where the disease is highly endemic. Goiter
and hypothyroidism are other manifestations of the deficiency. The
main risk factor involved is exclusive or nearly exclusive
consumption of locally grown foods in areas where the soil is
deficient in iodine.

Interventions include adding iodine to salt, tea, fish paste,
or bread, at a cost of US $0.02-0.04 per person per year for
iodized salt. Iodized oil is available in injectable or oral forms.
Interventions for iodine deficiency can also be combined readily
with interventions for vitamin A and/or iron deficiency. A new
assay is available to measure levels of thyroid hormone in samples
of blood from a fingerstick. Methods such as iodized salt were used
to eliminate iodine deficiency disorders more than 40 years ago in
Australia, England, New Zealand, Switzerland, and the United
States. Bolivia and Ecuador have almost eliminated the condition.
WHO has endorsed a goal of elimination of iodine deficiency
disorder by the year 2000. There is great need for improved
surveillance and estimates of the prevalence of these disorders and
of their economic impact. Iodine deficiency disorders can be
eliminated.

Neonatal Tetanus

WHO estimates that as of 1990 approximately 560,000 deaths
caused by tetanus infections in newborns occurred annually in
developing countries, mostly in Asia and Africa (34). Newborns are
infected by spores of the bacterium Clostridium tetani when the
umbilical stump is contaminated by unclean instruments or hands
used to cut the cord at birth and/or dressings applied to the area
in the first few days of the infant's life. The spores are found
widely in the environment, where they are associated with the feces
of ungulates. Most infected infants die of the disease.

Neonatal tetanus can be prevented by promoting clean
deliveries and by vaccinating women of childbearing age and
children. Based on this strategy, in 1989 WHO declared the goal of
eliminating neonatal tetanus by 1995. As of 1990, only about 58% of
women of childbearing age worldwide (43% in developing countries)
had received the two injections of vaccine required to protect
their infants. To achieve better control, the number of doses of
vaccine required to confer protection should be reduced and
surveillance of the disease and monitoring of vaccination coverage
should be improved. The reservoir of tetanus spores in the
environment is the major barrier to elimination of neonatal
tetanus, which cannot be eradicated. Preventing transmission of
this disease by continuing the interventions mentioned above,
however, is possible.

Onchocerciasis (River Blindness)

Onchocerciasis is caused by a parasitic worm, Onchocerca
volvulus, which is transmitted to persons by biting blackflies that
breed in fast-flowing rivers (25). The adult worms live for up to
15 years in nodules beneath the skin and muscles of infected
persons, where they produce millions of embryos (microfilariae)
that invade the skin, eyes, and other tissues. Some microfilariae
are taken up from the skin by blackflies to continue the
reproductive cycle. About 18 million persons are affected, mostly
in Africa (99%), Yemen, and Latin America. Both living and dead
microfilariae cause severe itching in the skin and sometimes
blindness after many years. Approximately 340,000 persons have
become blind from the disease.

Until the 1980s, the main control measure was to use
larvicides to kill immature blackflies in rivers. This method has
been used effectively by the multicountry Onchocerciasis Control
Program to reduce the incidence of the disease in part of West
Africa over the past 2 decades, but it is expensive. Since 1987,
the drug ivermectin has been provided by the manufacturer free of
charge to control programs for treating persons with
onchocerciasis. This treatment is effective in a single oral dose,
administered once annually; it prevents accumulation of
microfilariae in persons at risk. No drug suitable for mass
treatment can kill the adult worms in the host's body, and
onchocerciasis cannot be eradicated without such a means. The
blindness, however, can be eliminated.

Rabies

More than 50,000 persons die of rabies each year, mostly in
China and India (35). Humans are infected by saliva introduced into
wounds by the bite of a rabid wild or domestic animal, usually a
dog. Canine rabies is endemic throughout most of Asia, Africa, and
Latin America. Rabies also is endemic among some wild animals
(e.g., foxes, raccoons, skunks, and bats) in North America and
Europe. Rabies is almost always fatal.

Some developed countries have virtually eliminated rabies in
humans by mass vaccination of domestic dogs and destruction of
stray dogs. This approach is difficult to apply in rural areas of
most developing countries, where animals may not be privately
owned, destruction may be unacceptable, and such campaigns may be
expensive. Some Latin American countries are conducting successful
campaigns in cities, however. Attempts are being made to control
rabies in wildlife by development of oral vaccines that can be
safely distributed in baits. Eradication of rabies is not feasible,
primarily because of the extensive, varied animal reservoirs of the
virus and the inability to eliminate those reservoirs through
available technology. It is possible to eliminate human rabies in
urban areas, although the costs and benefits of doing so should be
considered.

Trachoma

Trachoma is a chronic inflammatory disease of the eye caused
by repeated infection with certain types of Chlamydia trachomatis,
which often results in blindness (36). Approximately 500 million
persons are infected worldwide, some 6-8 million of whom have
become blind. The disease progresses to blindness in about 5%-20%
of the infected population. It is transmitted mainly among children
and from them to women, perhaps during child care. Important risk
factors include low socioeconomic status and inadequate supplies of
water.

Effective interventions include mass treatment with
tetracycline ointment, which is effective in the short term. The
disease, however, usually returns within 6-12 months to
pretreatment levels in a community. Promotion of increased
face-washing and surgery of the scarred eyelids to prevent
continued damage to the cornea by turned-in lashes are other
interventions. There is need for more research into the costs and
benefits of interventions, the epidemiology of various risk
factors, and documentation of previous successes in control of the
disease. It appears scientifically feasible to eliminate blindness
caused by trachoma -- but not the infection or agent itself -- by a
combination of community-based education to promote face washing
and targeted antibiotic treatment.

Yaws and Other Endemic Treponematoses

Each year, approximately 2.5 million persons, mostly children,
contract yaws, endemic syphilis, or pinta -- all closely related
infections that are transmitted nonsexually, mainly by skin-to-skin
contact (37). These diseases rarely are fatal but often disfigure
or cripple affected persons by invading their skin, bones, and
cartilage. Endemic treponematoses occur in poor rural communities
in tropical Africa, Asia, or Latin America. All three diseases are
characterized by a positive serologic test that cannot be
distinguished from the positive test caused by venereal syphilis.
For each person with obvious skin lesions, two or more persons have
latent infections.

Mass treatment campaigns conducted during the 1950s and 1960s
with injectable penicillin pushed yaws almost to extinction. Yaws
and endemic syphilis have since resurged, especially in West
Africa. Serologic testing, treatment with penicillin, and
improvement in personal hygiene are the main interventions, all of
which could be implemented as a part of primary health care.
Similar infections have been seen in a few nonhuman primates but do
not appear to be epidemiologically important. Development of tests
to reliably distinguish these treponemes and their serologic
reactions would facilitate control efforts. The potential for
emergence of penicillin-resistant strains lends urgency to the need
for better control. Eliminating transmission of these diseases
seems feasible.

Diseases that Are Not Eradicable Now

Ascariasis (Roundworm)

Ascariasis, caused by the intestinal parasite Ascaris
lumbricoides (large roundworm), is one of the most common
infections of humans, affecting an estimated one billion persons at
any one time (38). It affects greater than or equal to 50% of
populations in tropical and subtropical areas. Its clinical effects
include respiratory or abdominal symptoms and discomfort, with or
without associated malnutrition, especially in young children.
Potential complications include obstruction of the bile duct by a
worm or, more commonly, intestinal obstruction by a mass of worms.
Globally, ascariasis causes an estimated 20,000 deaths per year.
Humans are infected when they ingest soil contaminated (by human
feces) with eggs of the parasite on their food, fingers, or drink.

An adult ascaris may live up to one and a half years. Humans
are the only reservoir, but the eggs may remain viable in soil for
years. Diagnosis requires careful examination of a fecal sample by
a trained microscopist. Control measures include sanitation and
education to promote using latrines, washing hands and food, and
avoiding use of uncomposted human feces as fertilizer; mass
chemotherapy; and provision of safe water for household use. Modern
anthelmintics administered in a single dose are safe and relatively
inexpensive and are effective for several months. Ascariasis is not
now eradicable, but it could be better controlled through mass
chemotherapy and hygiene education of schoolchildren.

Cholera

Cholera, characterized by severe watery diarrhea, dehydration,
and high mortality in untreated cases, is caused by the bacterium
Vibrio cholerae 01 (39). Many infections are asymptomatic. Although
cholera disappeared from much of the world in the 19th century, the
current pandemic of the El Tor cholera biotype has been exacerbated
by larger human populations, faster travel, and greater survival in
the environment. The disease has appeared in more than 100
countries in the past decade and greater than 70,000 cases were
reported to WHO in 1990, but the global prevalence of cholera is
unknown. It is associated with unsanitary conditions and may be
spread by fecal contamination of food, water, or hands. No
effective immunity develops.

There is no known animal reservoir, but foci of the organism
are now known to persist for years in aquatic environments in the
Gulf of Mexico and eastern Australia. The current vaccine gives
only limited protection for several months. Oral rehydration can
reduce mortality rates. Antibiotic drugs may shorten the duration
of illness and stop excretion of the vibrios. Cholera is not now
eradicable, although better control is possible by providing clean
water, sanitation, and health education. Priority research needs
are to understand the environmental reservoirs better (e.g., how
does the organism survive? are there other such foci?) and to
understand the molecular basis for differences among strains of V.
cholera.

Diphtheria

This disease, caused by infection with Corynebacterium
diphtheriae, is characterized by respiratory obstruction and/or
myocarditis as a result of a toxin released by some strains of the
bacteria. It is spread by direct contact and airborne droplets
(40). Less harmful infections of the skin occur more commonly in
developing countries. An asymptomatic carrier state may follow
infection. In the prevaccine era, diphtheria was a major cause of
illness and death in children in urban temperate areas. The global
toll is unknown, but cases reported to WHO declined from 77,000 in
1974 to less than 24,000 in 1988. It is not known if the
nontoxigenic strain of diphtheria induces immunity to infection.
Humans are the only reservoir.

The vaccine is an antitoxin, which usually is administered as
a part of the DTP or DT vaccines, in at least three doses
administered by injection at 1-month intervals. Booster doses are
also necessary. Widespread use of this vaccine has reduced the
incidence of diphtheria in developed and many developing countries.
In the United States, fewer than five cases were reported annually
during the 1980s. No cases were reported in Sweden for a 24-year
period. Recently, DTP vaccine has been used more widely in
developing countries. There has been a recent resurgence of this
disease in Russia. Diphtheria might be eradicable, but its effects
in developing countries and the epidemiologic impact of
immunization are not completely understood.

Hookworm Disease

Hookworm infections in humans are usually caused by
Ancylostoma duodenale or Necatur americanus, which together infect
an estimated 900 million persons in tropical and subtropical areas
(41). Local prevalence rates vary from 10% to 90%; they peak in the
later teenage years and among young adults. Infections become
clinically important when enough worms are present to cause anemia
from loss of blood as a result of the worms, which live in the
intestine. About 60,000 persons die of the infection annually, but
many infections do not cause symptoms. Hookworm is transmitted when
skin comes into contact with moist soil or vegetation that harbors
infective larvae hatched from eggs in the feces of an infected
person. Adult worms may live 1-5 years. Larvae in soil remain
viable for 3-4 weeks. Humans are the only known reservoir of this
infection.

Preventive measures and treatment are similar to those for
ascariasis, except that wearing shoes also protects against
hookworm larvae and administration of iron supplements can reverse
the resultant anemia. Sociologic barriers to control include the
association of the disease with poverty, poor personal hygiene and
defecation practices, and use of human feces as fertilizer -- all
factors that are difficult but not impossible to change. An attempt
to eradicate hookworm in the United States early in the 20th
century failed, and there is little or no political support for
another attempt. Hookworm is not now eradicable.

Leprosy (Hansen's Disease)

This chronic infectious disease caused by Mycobacterium leprae
affects an estimated 11-12 million persons worldwide (42). Leprosy
is usually nonfatal but may be severely disfiguring and disabling,
and affected persons are often ostracized. Prolonged contact with
an infected person is required for transmission. Wild infected
armadillos shed the bacteria into the soil and may transmit the
disease from animal to animal.

The introduction of sulfones for chemotherapy in the 1940s was
a major breakthrough, although many years of therapy were required
for cure. Combination therapy with two to three drugs has had a
major impact on the severity of the disease over the past decade.
The new drug regimens are shorter but still require 6-24 months of
therapy. Resistance of leprosy bacilli to chemotherapeutic drugs is
an increasing problem. China, Japan, and South Korea have rapidly
reduced the incidence and prevalence of this disease in recent
years. India and China established national programs with goals of
halting transmission of leprosy by 2000. In 1991, WHO set the goal
of eliminating leprosy (defined as incidence less than 1/10,000
population) worldwide by 2000. This disease is not now eradicable.
Impediments include absence of a fast, simple diagnostic test;
persistence of organisms, even in treated persons; cost and side
effects of drugs; duration of chemotherapy; patient compliance; and
the social stigma associated with the disease.

Measles

Almost a million persons, mostly infants and young children,
die annually from measles. Especially in Africa, it often leads to
death from pneumonia, diarrhea, and malnutrition (43). Measles is
highly contagious and spreads by airborne droplets exhaled by
infected persons up to 2 days before the characteristic rash
appears. Persons who recover are immune to reinfection for life.
The successful global campaign to improve vaccination levels by
1990 reduced the incidence of measles substantially. A single
injection of vaccine is usually sufficient to confer long-lasting
immunity, but to be effective it must be administered after the
infant's maternal immunity has waned.

Measles vaccine has been used to reduce the incidence of the
disease in the United States, Canada, Cuba, and some European
countries, but the disease has not yet been eliminated from any
large country. In 1977, the United States established the goal of
eliminating measles from the country by 1982. It reduced reported
cases to less than 3000 per year from prevaccine levels of greater
than 100 times that number, only to have the disease rebound to
25,000 cases in 1990. European and Caribbean countries plan to
eliminate measles by 1995. WHO has established the goal of reducing
the global incidence of measles by 90% by 1995. The ineffectiveness
of the vaccine for infants at birth or soon after and the high
degree of contagion of the infection are the principal barriers to
eradication of measles.

Pertussis (Whooping Cough)

This disease, caused by the bacterium Bordetella pertussis,
occurs worldwide (44). It primarily affects infants and young
children, with peak incidence in the first 2 months of life, and is
characterized by a severe, protracted cough. Globally, pertussis
still causes about 40 million cases and 400,000 deaths annually. It
is spread from person to person by direct contact and airborne
droplets and is highly contagious. Persons who recover are immune.
Humans are the only reservoir of the infection.

Pertussis vaccine is part of the combined
Diphtheria-Tetanus-Pertussis vaccine (DTP), which is administered
by injection and requires three to four doses to be effective. Use
of this vaccine has reduced pertussis incidence by more than 99% in
the United States since 1940. The high infectiousness of pertussis,
the occurrence of much of its impact within the first 2 months of
life, and the need to administer at least three doses of vaccine
(each dose at 1-month intervals) to achieve adequate protection are
major impediments to control. Better control could result from an
improved vaccine (e.g., fewer doses, greater efficacy, and safety
for adults), improved diagnostic methods, and study of the
epidemiology of pertussis in developing countries. If a safe
antigen were available for use in adults, researchers could
investigate the possibility of protecting infants by booster
vaccination of pregnant women. Pertussis is not now eradicable.

Rotaviral Enteritis

Some 80 million episodes of moderate to severe diarrhea and an
estimated 870,000 deaths per year are due to rotavirus, which is
the most common cause of severe diarrhea in children (45). It is
found in both developed and developing countries. The virus is
spread mainly by the fecal-oral route, but the mode of spread among
young children is uncertain. Some infections in India may originate
from cattle. Infection appears to protect children against
subsequent attacks of severe disease.

Improved hygiene, including handwashing, is the main available
mode of preventing spread of the disease. Use of oral rehydrating
solution can mitigate clinical effects. An effective vaccine is not
yet available for preventing this infection. Priority research
needs include development of an effective vaccine, studies of the
antigenic diversity of strains of the virus in developing
countries, development of an animal model, and further
investigation of mechanisms of immunity. Rotaviral enteritis is not
now eradicable.

Schistosomiasis (Bilharziasis)

Most human infections with this debilitating disease are
caused by Schistosoma mansoni, S. japonicum, or S. hematobium (46).
All three parasites, except possibly S. hematobium, have important
nonhuman reservoir hosts. About 200 million persons are affected in
Asia, Latin America, and especially Africa. Infection is usually
acquired in childhood, with peak prevalence and intensity among
persons 10 to 19 years of age. Untreated, chronic infection may
last 3-4 decades. Persons are infected when they enter fresh water
sources and larval forms of the parasite penetrate the skin. Such
sites are contaminated by egg-bearing feces or urine from infected
persons, allowing the worm to enter snails and multiply before
becoming infective to humans. Modern dams and irrigation projects
have often increased the habitat of the snails.

Modern mass chemotherapy has increased the potential for
control of this disease -- as demonstrated already in parts of
Brazil, China, and Egypt. Single oral doses of some anthelmintics
can decrease worm burdens for greater than or equal to 1 year,
depending on the drug and parasite species. Health education to
reduce contamination of and exposure to transmission sites and
provision of safe water and sanitary facilities are also vital.
Schistosomiasis is not now eradicable, but better control is
possible, especially by mass chemotherapy and hygiene education for
schoolchildren.

Tuberculosis

Tuberculosis (TB) infects 8-10 million persons and kills an
estimated 2-3 million annually (47). It occurs in all countries but
is an especial public health problem in many developing nations.
This bacterial infection is spread from person to person by
respiratory droplets, especially in crowded, poorly ventilated
conditions. Recently, its spread has been facilitated by the
concomitant infection of many patients with human immunodeficiency
virus (HIV).

Improved living conditions, case finding, drug treatment,
isolation of infectious patients, and selective chemoprophylaxis
reduced TB incidence in many industrialized countries in the 20th
century. Bacille Calmette-Guerin (BCG) vaccine has been used in
some countries to help protect infants and young children from
potentially fatal complications of TB. Emergence of strains of
Mycobacterium tuberculosis that are resistant to one or more of the
drugs used for treating the disease has complicated and hampered
control programs in the past few decades. In the late 1980s, the
United States declared a goal to eliminate TB in the country by
2010 (defined as an annual case rate of less than 1/1,000,000
population). There is need for more accurate, rapid diagnostic
tests; shorter and less expensive therapies; better case finding in
persons at risk; and a safer, more effective vaccine. It is not now
feasible to eradicate TB.

Yellow Fever

Yellow fever is believed to cause more than 10,000 deaths
annually in South America and Africa, but its incidence varies
because of sporadic epidemics, in addition to ongoing endemic
transmission of the disease (48). It is usually transmitted to
humans by bites of Aedes aegypti mosquitos in urban areas or by
bites of other mosquito vectors in sylvatic settings. A permanent
cycle of the virus is maintained in jungle-dwelling primates.

An effective vaccine has been available for more than 50
years, although it must be refrigerated and administered by
injection. It is recently being included in Expanded Programmes of
Immunization in some African countries, as recommended by WHO.
Research to improve the current vaccine would be helpful. More
aggressive use of the current vaccine could stop urban yellow fever
and reduce epidemics in rural areas. Because of the sylvatic
reservoir of infection, however, yellow fever cannot be eradicated.

Diseases that Are Not Eradicable

Amebiasis

Amebiasis is caused by the protozoan Entamoeba histolytica, a
parasite that usually lives in the large intestine of humans, who
are its only reservoir (49). Some 500 million persons may be
infected worldwide, of whom 38 million may develop serious
complications (e.g., liver abcess and colitis); 40,000-110,000
persons may die annually. The disease is associated with specific
strains of the parasite that have characteristic enzyme patterns.
It is especially prevalent in parts of Latin America, Africa, and
Asia. The infection is spread by ingestion of the hardy cysts on
food or hands or in contaminated drinking water. Most infected
persons are asymptomatic; some may excrete cysts for years.

Diagnosis usually requires examination of fecal specimens by
a skilled microscopist. Serologic tests and imaging techniques to
detect internal abcesses are also used. Drug therapy can eliminate
the parasite in the intestine and other organs, but most such drugs
must be administered for several days. Proper disposal of human
feces, education of persons at risk, and detection and treatment of
infected persons are key interventions. Amebiasis is not now
eradicable. Current barriers might be overcome if an effective,
safe drug became available that could be administered to large
groups in a single oral dose without prior testing. Control would
also be facilitated if it can be established that only amoebae from
symptomatic persons cause symptomatic disease in others.

Bartonellosis

This bacterial infection (Bartonella bacilliformis) is limited
to certain mountainous areas of Peru, Ecuador, and Colombia, where
it is transmitted by the bite of an infected sandfly (50). It also
can be transmitted by transfusion of blood from an infected person.
Infected persons may harbor the bacterium in their blood for many
years. The disease may manifest as severe anemia with fever or as
a painful skin eruption accompanied by pain in the muscles and
joints. The number of persons affected is unknown, but
approximately 40% of cases may be fatal and as many as 5% of
populations in areas where the disease is endemic may harbor
asymptomatic infections. Humans are the only known reservoir of the
infection. Persons may remain infective to sandflies for many
years.

The infection is diagnosed by microscopic examination of blood
or affected skin or by culturing blood on special media. Treatment
requires administration of high doses of antibiotics for at least
7 days. The risk of sandfly bites can be reduced by appropriate
insecticides and other protective measures. This infection is not
eradicable.

Clonorchiasis

This infection (caused by the parasite Clonorchis sinensis) is
endemic in parts of China, Japan, Korea, and Southeast Asia (51).
More than 20 million persons are infected in China alone. Persons
become infected by eating raw or inadequately cooked freshwater
fish (e.g., carp species or crayfish). In humans, the parasite
lives in the bile ducts, and its eggs are discharged in the feces,
sometimes for as many as 30 years. After the eggs are discharged,
the parasite must first enter a snail, then a fish as intermediate
host. Infection in humans is often asymptomatic, but it can cause
abdominal pain, gallstones, and cancer of the biliary tract. Pigs,
dogs, cats, and rats are also reservoirs of this parasite.
Transmission is most frequent, however, in areas where human feces
are used to fertilize fish ponds and where harvested fish are eaten
raw.

Diagnosis is made by identifying the eggs in fecal specimens,
but the eggs of a similar parasite (Opisthorchis) are identical.
Serologic testing is also helpful. Drug treatment for 1-2 days is
effective. Preventive measures include proper disposal of human
feces and thorough cooking or freezing of freshwater fish for at
least 5 days. This infection is not eradicable because of the
nonhuman reservoir, the many asymptomatic infections of humans, and
the fact that some infected persons can shed eggs for decades. Its
prevalence could be reduced, as with that of several other
infections, by promotion of sanitary disposal of human feces.

Enterobiasis (Pinworm)

Enterobiasis is an extremely common parasitic infection, often
of young children, in temperate and tropical countries (52). Humans
are the only hosts of the infection, which is caused by pinworm,
Enterobius vermicularis. The tiny adult worms live in the large
intestine for greater than or equal to 90 days. They deposit
larvae-containing eggs on or near the anus, where their presence
causes itching. Children are infected by putting fingers that have
been contaminated from scratching into their mouths or by inhaling
and then swallowing the eggs, which may become airborne with
household dust. The eggs can remain viable in the environment for
approximately 2 weeks. Associated pathology is unusual, but the
parasite may cause chronic appendicitis or invade the female
genital tract.

Diagnosis is made by identifying the microscopic eggs in
scrapings or on adhesive tape that has been pressed to perianal
skin. Several anthelmintic drugs are effective when administered in
a singe oral dose, but infected persons, their families, and other
close contacts usually should be treated simultaneously at least
twice, at 2-week intervals. It would be nearly impossible to arouse
support for the eradication of this widespread infection, since its
clinical effects are usually mild or nonexistent.

American Trypanosomiasis (Chagas' Disease)

Approximately 15-20 million persons in impoverished rural
areas of the Americas from Mexico to Chile are infected with the
parasite Trypanosoma cruzi (53). The infection is transmitted by
the bite of a triatomine bug ("kissing bug") or by blood
transfusion, after which there is a long latent period with few or
no symptoms. Manifestations may include swelling of the eyelid,
followed by fever and enlargement of the internal organs. Sudden
death due to acute cardiac problems can occur in infected young
adults. More than 150 species of domestic and wild animals are
hosts of this parasite, of which there are many strains. Many
epidemiologically important species of the insect vector live in
thatched roofs, cracks in walls, and other dark places.

Housing improvements to reduce suitable habitat for the insect
vectors and use of residual insecticides are the main bases for
preventive interventions in national control programs. Diagnosis,
whether by blood smear or serology, and treatment are difficult.
Improved diagnosis, methods for screening blood, and treatment are
needed. Chagas' disease is not eradicable at present.

Varicella (Chickenpox) and Zoster

Varicella-zoster virus causes two diseases: varicella, which
mainly affects children and causes generalized rash and fever; and
zoster, which produces a painful localized rash in adults when
latent infection from a prior attack of varicella is reactivated
(54). The virus is transmitted by the airborne route from sources
in the respiratory tract and skin. Varicella is highly contagious,
comparable with measles. Humans are the only reservoir of
infection, and most who recover are immune for life. The global
toll is unknown, but approximately three million cases of varicella
and 300,000 cases of zoster occur annually in the United States
alone, including about 100 reported fatal cases. Varicella appears
not to spread as much in tropical countries as in the United
States.

A live attenuated vaccine is expected to be licensed in the
United States soon, but it is not as effective as other common
live-virus vaccines. Moreover, the durability of such induced
immunity and its potential effect on the incidence of zoster are
unknown. Antiviral therapy with acyclovir can accelerate recovery
if it is administered early in the course of the disease. Immune
globulin is an effective prophylactic if administered soon after
exposure to the virus. The main barrier to eradication of this
disease is the ability of the virus to reactivate from latency to
produce zoster, which is about 25% as infectious as varicella. This
infection is not eradicable.

THE FUTURE

The concept and practice of disease eradication are now
accepted as useful, respected tools of international public health,
to be employed with scientific discretion. The likely achievement
of the next two declared targets for global eradication,
dracunculiasis by 1995 and poliomyelitis by 2000, together with the
precedent already established by the eradication of smallpox in
1977 (1 year later than the target date), should ensure the
survival and application of the principle of eradication
(Table_2). **
By the time dracunculiasis and poliomyelitis are expected to
have been eradicated, interim targets for measles (Table_4)
should
have been attained and progress should have been made toward the
control of other potential targets for eradication that have been
identified by the ITFDE (e.g., mumps, rubella, cyticercosis, and
lymphatic filariasis). Thomas Jefferson's "catalogue of evils" may
be steadily diminished with these attainments and with advances in
tools for controlling other potential targets such as
onchocerciasis (or Haemophilus influenzae b, for which conjugate
vaccines have been licensed).

If the epidemiologic benefits of eradication are not incentive
enough, the fiscal rewards may help ensure the concept's
acceptability. The United States alone has been recovering its
total investment of about $30 million in the global Smallpox
Eradication Program every 3-4 months since the early 1970s. Since
smallpox was eradicated in 1977, that total investment has been
returned to the United States every 26 days. Based on the current
rate of progress towards eradication of poliomyelitis, WHO predicts
that campaign will "produce {global} savings of half a billion
dollars by the year 2000, increasing to U.S. $3 billion annually by
the year 2015."

The main obstacle to the concept's current acceptance is that
if the concept of eradication is invoked against inappropriate or
unattainable targets, it can again be brought into disrepute. The
declared targets of "elimination" of neonatal tetanus by 1995 and
of leprosy by 2000 are potential examples of such dangers. Care
should be taken to reserve use of the terms "eradication" and
"elimination" only for carefully chosen diseases that have a high
likelihood of being eradicated.

Continued advocacy is required to maintain appropriate
consideration of the issues considered and suggestions made by the
ITFDE. The Task Force for Child Survival and Development, which
includes several key members of the ITFDE, will review updates of
this topic annually. If new information or the appearance of new
control measures, for example, suggest the need for it, a group may
be reconvened to consider other diseases in depth (e.g., H.
influenzae b) or reconsider diseases that were discussed by the
ITFDE. In the interim, the most urgent task for promoting the
concept of disease eradication is to ensure the successful
eradication of dracunculiasis by 1995 and of poliomyelitis by 2000.

Acknowledgment

The International Task Force for Disease Eradication (ITFDE)
was established in 1988 to systematically review potential
candidate diseases for eradication and to provide leadership and
advocacy for the concept of eradication where appropriate and
useful. The secretariat for the ITFDE was supported by a grant from
the Charles A. Dana Foundation to William H. Foege, M.D., M.P.H.,
then the Executive Director of the Carter Center of Emory
University.

Langmuir AD. Prospects for eradication of viral diseases by
immunization. In: Proceedings of the International Conference
on
the Application of Vaccines against Viral, Rickettsial, and
Bacterial Diseases of Man. Washington, DC: Pan American Health
Organization, 1970.

Gershon AA, ed. The First International Conference on the
Varicella-Zoster Viruses. J Infect Dis 1992;166(suppl 1):51-68.

* The summaries were prepared by the project director, based on the
working papers presented to the Task Force. The original authors
have not reviewed these summaries. Incidence data for several
diseases have been updated. A single reference is provided for
each
summary as a suggestion for further reading.

** The full text of the World Health Assembly resolutions regarding disease eradication is available on request to the World Health
Organization.

APPENDIX_1
Table_A1Table_1Note: To print large tables and graphs users may have to change their printer settings to landscape and use a small font size.

TABLE 1. Criteria for assessing eradicability of diseases and conditions
======================================================================================
Scientific Feasibility
. Epidemiologic vulnerability (e.g., existence of nonhuman reservoir; ease of
spread; natural cyclical decline in prevalence; naturally induced immunity;
ease of diagnosis; and duration of any relapse potential)
. Effective, practical intervention available (e.g., vaccine or other primary pre-
ventive, curative treatment, and means of eliminating vector). Ideally,
intervention should be effective, safe, inexpensive, long-lasting, and easily de-
ployed.
. Demonstrated feasibility of elimination (e.g., documented elimination from
island or other geographic unit)
Political Will/Popular Support
. Perceived burden of the disease (e.g., extent, deaths, other effects; true bur-
den may not be perceived; the reverse of benefits expected to accrue from
eradication; relevance to rich and poor countries).
. Expected cost of eradication (especially in relation to perceived burden from
the disease).
. Synergy of eradication efforts with other interventions (e.g., potential for
added benefits or savings or spin-off effects)
. Necessity for eradication rather than control
======================================================================================

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